Four huge asteroids — and a fifth that's much smaller — are passing Earth on Thursday in their closest approaches to the planet ever recorded.

Four "potentially hazardous" space rocks, which are between 100 and 580 feet across, will all make their closest approaches to Earth within less than 12 hours of one another on Thursday (Oct. 24). Two of them were only discovered earlier this month.

A city-sized asteroid is approaching Earth this October, set to make its closest approach on October 27. Known as 1036 Ganymed, this is one of the largest near-Earth asteroids, with a diameter of approximately 37.7 kilometres, comparable in size to Houston, in the US.

Four enormous asteroids, including one with the potential to wipe out an entire city off the map, are making a close flyby of Earth on Thursday. Deemed potentially hazardous, each will come within 30 miles of our planet in just a span of 12 hours.